Antioxidant composition



United States Patent Ofiice 3,347,938 Patented Oct. 17, 1967 This invention relates to antioxidants and more particularly to a new class of compounds having structure and properties which render them especially useful as antioxidants for various polyolefines such as polyethylene, polypropylene and poly-butane, parafiin wax and various other oxidizable organic materials. More especially the invention relates to a special class of 2,4,6-triall-;ylated phenols in which all of the alkyl groups contain long branched chains.

The use of alkylated phenols such as 2,6-di-t-butyl-pcresol as antioxidants for polymers and other oxidizable organic materials is well known in the art. The substances can be represented by the following structure:

Past experience has shown that R and, often, R must be tertiary alkyl groups to make I a potent antioxidant. On the other hand, it has been generally agreed that R must be either methyl or hydrogen or the potency is greatly decreased. For example, although 2,6-di-t-butylp-cresol (R R t-butyl, R =CH and 2,6-di-t-butylphenol (R :R =t-butyl, R =H) are quite effective antioxidants, 2,4,6-tri-t-butylphenol (R :R :R :t-butyl) is almost completely ineffective. Thus it would be totally unexpected that compounds such as II (below) would be effective antioxidants. Not only are R and R in this structure not tertiary but R is a long alkyl group. From all past experience such a compound would be expected to be relatively inactive as an antioxidant.

We have now made the surprising discovery that compounds having structure II wherein the three substituents are all long secondary alkyl groups are unexpectedly potent antioxidants in a wide variety of oxidizable organic substances. Such compounds are represented by the structural formula:

wherein R =CH C H C H straight chain alkyl groups and 2= i0 2n 11 23 12 25, ta m ri zs, 15 31, C H C H C I- straight chain alkyl groups and wherein R +R =C H to C H and consist of saturated alkyl groups. Furthermore, we have made the equally surprising discovery that analogs of structure II in which the substituent alkyl groups are tertiary such as Compound III (below) are almost completely inefiective as antioxidants:

l CH Ila nIIlo III It is accordingly the principal object of the present invention to provide a new class of antioxidants having structures and properties which render them especially useful as antioxidants for various polyolefines such as polyethylene, polypropylene and polybutylene, paralfin wax and various other oxidizable organic materials.

Another object is to provide a new class of alkylated phenols useful as antioxidants for the materials referred to in the preceding paragraph.

A specific object is to provide a new class of highly effective antioxidants 2,4,6-trialkylated phenols in which all of the alkyl groups contain long branched chains which are saturated alkyl groups.

Other objects will appear hereinafter.

These objects are accomplished by the invention described herein and illustrated by the examples that follow. In its broad aspects and as set forth above, the invention is based upon the discovery that when all three substituent groups of 2,4,6-trialkyl phenols are long secondary alkyl groups these alkylated phenols have remarkable antioxidant potency when employed in polymeric substances such as olyethylene, polypropylene, polybutylene, parafiin waxes and other oxidizable organic materials which are subject to oxidative decomposition and degradation especially under thermal influences. As indicated above, our new antioxidants are 2,4,6-trialkylated phenols which may be represented by the structural formula:

wherein R =CH C H C H straight chain alkyl groups and 2= 10 2n n zs, 12 z5 CIEHZ'I u zs, 15 s1, C H C H C H straight chain alkyl groups and wherein R -l-R C H to C H and consist of satu rated alkyl groups.

We believe our new antioxidants to be largely the structure predicted from the following equation:

wherein R is an alkyl group.

C 11 C 11-0 11 ii -R.

etc. This rearrangement would result in the formation of some proportion of alkylated phenol in which some or all of the substitucnt groups would have structures such as C2H5 Call? G1IC[[ R-L II-R etc. Therefore, we do not preclude the possibility that the antioxidants herein described are mixtures of isomeric compounds differing in the configuration about the 0:- carbon atom of the substituent alkyl groups. However, such isomers would all contain only secondary alkyl substitution and would be described by structure 11. Present analytical techniques are incapable of separating such isomers or demonstrating unequivocally their presence or absence in our new antioxidants.

In the following examples and description we have set forth several of the preferred embodiments of our invention but they are included merely for purposes of illustration and not as a limitation thereof.

EXAMPLE I Preparation of 2,4,6tris(I-methylheptadecyl)phenol Boron tritiuoride gas was passed into 94 g. (1.0 mole) of phenol until 12 g. had been absorbed. The mixture was then heated to 85 C. and to it was added over 45 minutes 762 g. (3.0 moles) of l-octadecene. The temperature was held at 8285 C. by heating as required. Heating at this temperature was continued for an additional 2 hours. The mixture was then cooled and dissolved in 1 l. of hexane. The hexane solution was washed once with 1 1. of water, twice with 5 percent aqueous sodium acetate and twice more with water. The hexane was evaporated and the residue stripped under vacuum to a base temperature of 260 C. at 1 mm. pressure. The residue was molecularly distilled in a falling film still to give 710 g. of amber moderately viscous oil, distilling at 217-220 at 1 micron pressure which has a molecular weight of 830 and was identified as 2,4,6-tris(l-methylheptadecyl) phenol (C H O, calculated molecular weight 856).

EXAMPLE II Preparation of 2,4,6-tris(I-methylnonadecyl)phenol Following the method of Example I, 94 g. (1.0 mole) of phenol was alkylated with 840 g. (3.0 moles) of 1- eicosene. After isolation as in Example I molecular distillation gave 850 g. of viscous amber oil distilling at 235-250 C. at 1 micron and having a molecular weight of 895. The molecular weight calculated for C H O is 934.

EXAMPLE III Preparation of 2,4,6-tris(I-methylzmdecyl)phenol.

Following the same procedure as in Examples I and II, 94 g. (1.0 mole) of phenol was alkylated with 504 g. (3.0 moles) of l-dodecene. The product, isolated and purified as before, was an amber viscous oil, BR 160 170 at 2 microns. The molecular weight was found to be 585. The calculated molecular weight for C H O is 598.

The compounds of our invention were tested for antioxidant effectiveness in a number of polymeric substances subject to decomposition or degradation under oxidative influences and were found to be extremely effective. A

description of such tests and the results obtained are set forth below.

Antioxidant efircrivcness of compounds in polypropylene The subject antioxidants were incorporated in polypropylene at the 0.3 percent level by milling in a Banbury mixer. These samples, in the form of approximately 41 inch thick strips, were evaluated by the 160 C.-oven test and C. stress crack test. The C.-oven test is carried out by exposing the samples in an air oven at 160 C. until the first appearance of peroxide as shown by the usual iodiometric test. In the stress crack test the samples are bent in the shape of a U by inserting in a slotted metal holder and then exposed in an air oven at 140 C. until visual examination shows the presence of surface-cracks. The results of these tests are shown in Table 1.

TABLE 1 160 Oven Lire, hrs.

140 Stress Crack Life, hrs.

Antioxidant L trisalkylated phenol 1 g propylenetutramer trisalkyluted pllenoW.

0.3% i-hut yluuetrimer trisalkylated phenols 3 1 Alltylnlvrl with Enjny Chemicals Company a-olvtin mixture containing about equal quantities of 1-hoxudvueue, l-lu-ptn- (IPCIIH, l tlf'llllltfllll. l lltlllildttit'lle and 1 uiconenr'.

S00 Structuri- .IlI.

Similar to Strut-turn III, 1.0., all alkyl groups are tertiary Ciallun-bltllfl'lilll ulkyls.

Antioxidant efiectiveness of compounds in polyethylene The subject antioxidants were incorporated in polyethylene at the 0.5 percent level by milling as described for polypropylene. Samples were evaluated by exposure in an air oven at 160 C. until an increase in peroxide concentration occured. The results are reported in Table 2.

TABLE 2 Antioxidant: 160 C. oven life hrs.

None 2 0.3% 2,4,6-tris(l-methylnonadecyl) phenol 25 0.3% 2,4,6-tris(l-methylpentadecyl) phenol 20 0.3% 2,4,6-tris(1-methylundecyl) phenol 18 0.3% 2,4,6-tri-t-butyl phenol 2 0.3% propylenetetramer trisalkylated phenol 1 3 1 Sec Structure III.

Antioxidant efiectiveness of compounds in poIy-l-butcne The subject antioxidants were incorporated in polylbutene by milling. Samples were evaluated by the 160 C. oven test as described above. The results are summarized in Table 3.

Antioxidant efiecriveness of compounds in a 1 r0 I (:0 polymer of propylene and I-butene The antioxidants were incorporated and evaluated as previously described using the 160 C. oven test. The results are summarized in Table 4.

TABLE 4 Antioxidant: 160 C. oven life hrs.

None 0.4 1% 2,4,6-tris(l-methylhcptadecyl) phenol 7 1% 2,4,6-tris(l-methylundecyl) phenol 5 1% 2,4,6-tri-t-butyl phenol 0.4

1% propylenetetramer trisalkylated phenol 0.4

1 See Structure III.

Antioxidant efiectiveness of compounds in parafiin wax The subject antioxidants were incorporated in paralfin wax at the 0.05 percent level by mixing with the molten wax. Air was bubbled through the molten wax at the rate of 2.33 ml./sec. at 150 C. and the time required for the build up in peroxide to 20 milliequivalents per kilogram was reported as the AOM value. The results are tabulated in Table 5.

TABLE 5 Antioxidant: AOM value hrs.

None 3 0.05% 2,4,6-tris(l-methylheptadecyl) phenol 180 0.05% 2,4,6-tris(l-methylundecyl) phenol 110 0.05 2,4,6-tri-t-butylphenol 8 0.5% propylenetetramer trisalkylated phenol 1 4 1 See Structure III.

embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

6 We claim: 1. A new class of chemical compounds having antioxidant properties having the structural formula:

wherein R =CH C H C H straight chain alkyl groups and 2= 1o 2b u 23 12 2s 13 2'1 u za lS SIr C H C H C H straight chain alkyl groups and wherein the sum total of the carbon and hydrogen atoms of the R +R moieties is in the range Of from C11H24 to CHI-I40.

2. The compounds of claim 1 in which the sum total of the carbon and hydrogen atoms of the R -l-R moieties is C17H35.

3. The compounds of claim 1 wherein the sum total of the carbon and hydrogen atoms of the R +R moieties is 15 31- 4. 2,4,6-tris(l-methylheptadecyl)phenol.

5. 2,4,6-tris(l-methylpentadecyl) phenol.

6. 2,4,6-tris(l-methylnonadecyl) phenol.

References Cited UNITED STATES PATENTS 2,202,877 6/1940 Stevens 260--624 LEON ZITVER, Primary Examiner.

BERNARD HELEFIN, Examiner.

W. B. LONE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,347,938 October 17, 1967 Alan Bell et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column L, TABLE 1 footnote 3, line 2 thereof, for

C H d 42 2S rea ClZHZS Signed and sealed this 17th day of December 1968 (SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A NEW CLASS OF CHEMICAL COMPOUNDS HAVING ANTIOXIDANT PROPERTIES HAVING THE STRUCTURAL FORMULA: 